1. Field of the Invention
This invention relates to a power receptacle, and in particular, it relates to a receptacle with a safety shutter providing tamper resistance.
2. Description of the Related Art
Conventional power receptacle such as wall receptacles or extension cord receptacles have one or more holes to receive plugs. The electrical conductors in open holes may corrode due to the moisture in the air, or their electrical conductivity may be affected by dust accumulation. Moreover, if used improperly, or if children play with the receptacle, conductive foreign objects may be inserted into the hole. This can cause electrical shock and is of great safety concern.
To solve the above problem, tamper resistant receptacles have been developed. However, these tamper resistant receptacles have various shortcomings.
For example, in the tamper resistant receptacle described in U.S. Pat. No. 4,379,607, a plastic biasing member is used at each end of the device to urge the shutter to the closed position. Such plastic biasing members tend to be unreliable as the material may become fatigued due to repeated use and various environmental factors. Thus, the elasticity of the plastic material may be lost and the shutters may fail to close. Further, the plastic biasing members are bulky and increase the overall size of the receptacle.
As another example, in the tamper resistant receptacle described in U.S. Pat. No. 5,915,981, a coaxially disposed compression coil spring is used at each end of the device to urge the shutter to the closed position. Such springs also tend to be bulky.
As another example, in the tamper resistant receptacle described in Chinese patent CN 99254384.3, the biasing member used in the safety mechanism is an F-shaped metal plate, which tends to become fatigued or broken due to repeated use. Further, the biasing member and the safety mechanism are installed separately, making it inconvenient to install and replace and limiting its applicability.
Some other tamper resistant receptacles have complicate structures and are costly to manufacture.